An extensive collection and review of the published literature and reports on various aspects of epidemiology of Headache has been carried out in FY 1980. Strengths and inadequacies of the published information about prevalence, the characteristics of the afflicted population and the identification of risk factors that may be associated with both the occurrence of the headache syndrome or with its acute exacerbations were summarized and evaluated. Research approaches which can provide improved data for approaching the clinical issues of etiology, prevention and therapy were suggested. An invited paper of the review work was presented at the International Headache symposium 1980 in Florence, Italy, in March, 1980.